U.S. patent application number 12/127518 was filed with the patent office on 2009-12-03 for anti-icing material and surface treatments.
This patent application is currently assigned to Appealing Products, Inc.. Invention is credited to Amir J. ATTAR.
Application Number | 20090294724 12/127518 |
Document ID | / |
Family ID | 41378630 |
Filed Date | 2009-12-03 |
United States Patent
Application |
20090294724 |
Kind Code |
A1 |
ATTAR; Amir J. |
December 3, 2009 |
ANTI-ICING MATERIAL AND SURFACE TREATMENTS
Abstract
An anti-icing composition including a chemically-bound
nano-layer based on a multivalent atom such as silicon or titanium,
and whiskers of hydroxyls, polyols, polyethers, polyamines,
poly-acids or mixtures of such hydrophilic functionalities. This
base layer may be used as such or have an additional coating
overlying it, e.g., comprising a polymeric polyol such as
polyvinylalcohol or polyglycol. The second layer may also be
chemically bonded to the surface or to the first layer. Surface
treatment with such composition prevents small droplets of water
from freezing on the surface and reduces dramatically their
friction with the surface. The result is the prevention of icing of
the surface, reduction in the adhesion of ice to the surface and
reduction in the accumulation of ice layers. The anti-icing
composition also makes removal of ice from the surface much easier
once accumulated, and is useful in reducing de-icing requirements
of aircraft and in retarding in-flight ice formation. Other
applications include coating window panels and vehicles exposed to
icing conditions and preventing bulk particles from adhering to
each other in icy conditions.
Inventors: |
ATTAR; Amir J.; (Raleigh,
NC) |
Correspondence
Address: |
INTELLECTUAL PROPERTY / TECHNOLOGY LAW
PO BOX 14329
RESEARCH TRIANGLE PARK
NC
27709
US
|
Assignee: |
Appealing Products, Inc.
Raleigh
NC
|
Family ID: |
41378630 |
Appl. No.: |
12/127518 |
Filed: |
May 27, 2008 |
Current U.S.
Class: |
252/70 ; 106/13;
244/134E |
Current CPC
Class: |
C09D 183/04 20130101;
C09K 3/18 20130101 |
Class at
Publication: |
252/70 ;
244/134.E; 106/13 |
International
Class: |
C09K 3/18 20060101
C09K003/18 |
Claims
1. An anti-icing composition layer on a substrate surface,
comprising a polymeric layer chemically bonded to the surface with
multiple hydrophilic, hydroxylic or ionic groups attached to the
polymer of said polymeric layer or to grafted appendages on the
polymeric layer.
2. The anti-icing composition layer on a substrate surface
according to claim 1, wherein the layer is chemically bonded to the
surface by multivalent element-oxygen-to-surface bonds and wherein
the multivalent atom is selected from the group consisting of
silicon, carbon, tin, titanium, germanium, zirconium, hafnium,
vanadium and carbon.
3. The anti-icing composition layer on a substrate surface
according to claim 1, wherein the multivalent element is selected
from the group consisting of silicon, titanium and zirconium.
4. The anti-icing composition layer on a substrate surface
according to claim 1, wherein the polymeric layer comprises a
polymer formed by monomers containing hydrolysable mono, di or
tri-X-silicones wherein each X is independently selected from the
group consisting of chlorine, bromine, iodine, acrylates,
methacrylates, aryl-sulfonates, alkyl-phosphates, ethylene amines,
aliphatic acids, aliphatic hydroxy acids, alkoxy groups, methoxy,
ethoxy, iso-propoxy, di-silazanes, hydrolysable nitrogen moieties,
hydrolysable sulfur moieties, and hydrolysable phosphorous
moieties.
5. The anti-icing composition layer on a substrate surface
according to claim 1, wherein the polymeric layer comprises a
polymer formed by monomers containing two or more terminal
tri-X-multivalent element groups, wherein X is a hydrolysable
group.
6. The anti-icing composition layer on a substrate surface
according to claim 1, wherein the polymeric layer comprises a
polymer formed by monomers containing a mixture of
di-tri-X-multivalent element and mono-tri-X-multivalent element
compounds.
7. The anti-icing composition layer on a substrate surface
according to claim 1, wherein the multivalent element in the
monomers containing hydrolysable tri-X-multivalent element is also
attached to a reactive organic radical.
8. The anti-icing composition layer on a substrate surface
according to claim 7, wherein the organic radical is selected from
the group consisting of chlorine, bromine, iodine, epoxide,
carbonyl, nitrile, cyano, amine-including aromatic or aliphatic
primary, secondary, tertiary and quaternary amines and their salts,
chlorides, bromides, sulfates, nitrile, amides, esters, ethers,
alkoxy, methoxy, ethoxy, thioalkyl, epoxide, vinyl, phosphine,
phosphates, sulfonic and halo-sulfonic groups.
9. The anti-icing composition layer on a substrate surface
according to claim 1, wherein the polymeric layer is deposited on
the surface by first partially hydrolyzing a tri-X-multivalent
element, and applying the resulting partially-hydrolyzed mixture to
the surface.
10. The anti-icing composition layer on a substrate surface
according to claim 1, wherein the polymeric layer is sprayed onto
the surface for coating thereof.
11. The anti-icing composition layer on a substrate surface
according to claim 1, further comprising a secondary coating on the
polymeric layer to increase its hydrophilicity.
12. The anti-icing composition layer on a substrate surface
according to claim 11, wherein the secondary coating includes
multi-hydroxy, poly-carboxy or poly-amino polymeric compounds
selected from the group consisting of poly vinyl alcohol and its
homologs, poly ethylene glycol and its homologs, polyacrylic acid
and its homologs, polyimines, polyamines and polymeric salts.
13. The anti-icing composition layer on a substrate surface
according to claim 1, wherein the surface is a pretreated
surface.
14. The anti-icing composition layer on a substrate surface
according to claim 13, wherein the pretreated surface has been
pretreated by a technique selected from among: (a) functionalizing
the surface with hydroxy, carboxy, carbonyl, carbonyls, amino or
sulfonic groups to increase bonding of monomers of the polymeric
layer to the surface; (b) contacting the surface with an alkaline
base selected from the group consisting of sodium hydroxide,
potassium hydroxide, ammonium, and calcium hydroxide; (c)
contacting the surface with an aqueous solution of an alkaline salt
including a cation selected from the group consisting of sodium,
potassium, calcium, lithium, cesium, and rubidium, and an anionic
moiety selected from the group consisting of phosphate, carbonate,
sulfide, borate, acetate, organic sulfonate, and organic phosphate;
(d) contacting the surface with an organic amine; (e) contacting
the surface with an aqueous solution of an oxidizer selected from
the group consisting of permanganate, chromate, persulphate,
perphosphate, and peroxide; (f) contacting the surface with a
solution of a metalite complex selected from the group consisting
of sodium naphthalene and potassium naphthalene; and (g) contacting
the surface with an aqueous solution of a reducing agent selected
from the group consisting of titanium trichloride and tin
chloride.
15. The anti-icing composition layer on a substrate surface
according to claim 13, wherein the pretreated surface has been
pretreated by a technique selected from among oxidation of the
surface, oxidation of the surface followed by hydrolysis,
introduction of ions onto the surface via acidic or amino groups,
and functionalizing the surface with carbonyl or epoxide
groups.
16. The anti-icing composition layer on a substrate surface
according to claim 7, wherein a second treatment is used to
activate the reactive organic radical and wherein the activation
comprises one or more of hydrolysis, oxidation and diazotation.
17. The anti-icing composition layer on a substrate surface
according to claim 16, wherein a third reaction is used to couple a
multi-hydroxy compound to the activated organic radical and wherein
the third reaction is selected from the group consisting of
etherization, esterification, diazo-coupling and formation of a
salt.
18. The anti-icing composition layer on a substrate surface
according to claim 1, wherein the anti-icing composition layer is
cured by hot air in a temperature range of 25 to 300.degree. C.,
for a period of from 0 to 120 minutes.
19. The anti-icing composition layer on a substrate surface
according to claim 1, wherein the anti-icing composition layer is
cured at temperature in a range of 120-170.degree. C. and duration
of curing is in a range of 5 to 30 minutes.
20. The anti-icing composition layer on a substrate surface
according to claim 1, wherein monomer of said polymeric layer is
hydrolyzed in a pH range of 1 to 8.
21. The anti-icing composition layer on a substrate surface
according to claim 1, wherein monomer of said polymeric layer is
hydrolyzed in a temperature range of 0 to 60.degree. C., in an
aqueous solution in which concentration of the monomer is in a
range of from 0.001 to 20% by weight, based on total weight of the
solution.
22. The anti-icing composition layer on a substrate surface
according to claim 1, wherein monomer of said polymeric layer is
selected from among N-(3-Triethoxysilyl propyl) gluconamide,
tris(acrylic acid) titanium ethoxylate,
2-[Methoxy(polyethyleneoxy)propyl], and neopentyl(dially)oxy
tris(acrylic acid) zirconate.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to compounds and coatings
comprising same, which are usefully employed on surfaces to reduce
or prevent the formation of ice layers on them and/or facilitate
the removal of ice by other means, as well as to associated
methodology for the use of such compounds and coatings, e.g., on
aircraft and other vehicles.
BACKGROUND OF THE INVENTION
[0002] Ice formation on aircraft has been the cause of multiple
fatal accidents and loss of property. Thus, it is desirable to find
means and methods to prevent or reduce ice formation on aircraft
and on other vehicles.
[0003] Accumulation of ice on wings of an aircraft changes the
aerodynamics of the wing, and has an adverse effect on the lift
produced. Moreover, ice buildup on aircraft wings increases the
drag on the aircraft by 30-80%, thus reducing fuel efficiency and
increasing the cost of aircraft operation. Additional problems may
occur if an ice layer forms on the air intake shutters or across
stabilizer fins, such as engine stalling. If the fins are wholly
unable to operate, the pilot may lose control of the aircraft.
Moreover, even if the wings or fins were ice-free on take-off,
flying through ice storms or supersaturated clouds can result in
ice buildup on an aircraft. In-flight buildup of ice can prevent
air shutters or navigation gear from moving, cause air filters to
freeze etc., which in turn reduces the ability of the pilot to
maneuver or control the aircraft.
[0004] Ice buildup on unmanned aircraft has also proven to be
extremely dangerous and the cause of numerous failures of such
craft. This is due in part to the fact that such aircraft are
typically made out of composites, that these aircraft have very
little surplus energy to combat deicing and that they lack the
on-board supervision of a pilot. Instances are documented in which
icing resulted in engine shut-down and aircraft failure.
[0005] In addition to the foregoing, ice buildup on turbine blades
of aircraft engines reduces their efficiency, and can result in
damage to the blades. In extreme cases, such icing of the engine
turbine blades can result in the downing of the aircraft.
[0006] Many methods have been devised and some are being routinely
used to remove ice/snow from wings and from other parts of
aircraft, to reduce the likelihood of accidents. Unfortunately,
these methods involve the use of chemicals, heat, hot washes and
other energy-intensive and/or environmentally hazardous means.
Moreover, the removal of ice from stationary aircraft in an airport
setting is not done under strict time pressures and other
constraints that are characteristic of in-flight deicing. On ground
deicing typically uses much more material, energy and manpower than
in-flight deicing. The need for in-flight deicing has motivated
efforts to develop anti-ice technologies that are effective to
prevent the accumulation of ice or reduce it significantly, yet do
not require excessive amounts of energy and materials, or
expensive, complicated or heavy hardware.
[0007] Despite such efforts, an effective technical solution has
not yet been found. Various studies have shown that certain surface
coatings can temporarily reduce ice formation on aircraft in
flight. Unfortunately, these coatings are susceptible to being
irreversibly damaged by water, rain and even ice, in addition to
being expensive, hard to repair if damaged, and having only a
limited life.
[0008] It would therefore be a significant advance in the art to
provide an effective means and methodology for combating icing of
surfaces and components of aircraft and other objects that are
susceptible to icing.
SUMMARY OF THE INVENTION
[0009] This invention relates to various classes of materials that
can be bound to a solid surface to confer to it anti-icing
properties. In addition, it relates to various methods to
chemically bind such anti-icing compounds to the surface, and
methods to enhance the strength and the density of chemical bonds
between the anti-icing coatings and the solid surface.
[0010] The
[0011] Other aspects, features embodiments of the invention will be
more fully apparent from the ensuing disclosure and appended
claims.
DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS
THEREOF
[0012] The present invention relates to compositions and methods
for combating icing of surfaces and objects that are susceptible to
icing and deleteriously affected by same, e.g., surfaces and
components of aircraft.
[0013] The invention contemplates the formation of ice-combating
layers that are stable, low in cost, repairable, and easy to apply.
Such layers are highly effective, particularly when the
temperatures are not excessively low, and can prevent ice formation
altogether in many cases. Since many aircraft are most vulnerable
to icing on take off and landing, when the icing conditions are
relatively mild, the ice-combating compositions of the invention
are highly attractive for application to aircraft wings and other
components of such craft.
[0014] When super-cooled droplets of water impinge on moving,
inclined solid surfaces at sub-freezing temperatures, the droplets
may deliver their enthalpy of freezing and immediately solidify,
may move on the surface up or down the incline and solidify, or may
leave the surface, depending on the relative speeds of the air and
the solid, the angle of inclination and the gravity force, the
droplet size, the relative temperatures and other variables. The
droplets may also shatter into smaller droplets that freeze
instantly, glide some distance and then freeze or glide along the
entire length of the surface and leave without freezing. It is
desired that as much as possible of the liquid water that impinges
on the surface will leave it without solidifying, i.e., without
freezing on it.
[0015] The surface coatings of the present invention modify the
icing of moving surfaces in two major ways: (i) they retard the
nucleation of ice crystals on the surface and thus retard the
formation of the ice phase, and (ii) they reduce drastically the
friction coefficient between the liquid water and the surface and
thus allow the water to move and disengage from the surface before
it has time to freeze.
[0016] The present invention contemplates materials that inhibit
the nucleation of water by preventing assembly of molecules on the
surface to form ice nuclei, and anchor molecules to surfaces to
form stable, water-insoluble layers. When the nucleation is
prevented, delayed, or inhibited, liquids can be cooled down to
much lower temperatures than their normal solidification
temperatures and still remain fluidic. This phenomenon is known as
supercooling. Supercooling can be achieved to some extent with all
materials. Dissolving salts and other materials in liquids,
including water, lower their freezing points, i.e., their
solidification temperatures, and help in keeping them liquids.
[0017] The present invention provides a surface coating that
interferes with the nucleation of ice on a surface, and methods for
forming such surface coatings. The ice-inhibiting coatings of the
invention are bound chemically to the surface and not used as a
simple overlay coating.
[0018] In respect of the invention, a thin layer of material that
can imbibe water and that covers the surface of a solid, absorbs
water and forms a thin solution layer. The freezing temperature of
this solution is below the freezing point of ordinary water, since
the immobilized solute inhibits the nucleation of ice particles. As
long as the water in the coated layer remains liquid, liquid water
will not adhere to it and freeze, and ice layers will not form or
grow on it, until a much lower temperature is reached than the
normal freezing temperature of water. If a very high load of water
impacts and totally covers the surface, it may freeze independently
of the coating layer. This may in turn allow "sloughing" of the
independently frozen water from the underlying coating layer, so
that the surface is less impacted by the high water loading than
would be the case if the substrate surface were uncoated with the
coating material of the invention.
[0019] The effectiveness of the surface coating of anti-icing
material depends on its ability to imbibe water. Since all the
materials that can dissolve or imbibe water are also at least
partially water soluble, some of the anti-icing coating may be lost
unless the coating is anchored to the solid surface. If the
protective layer is not attached to the surface, excessive water
will gradually dissolve and remove it and it will have to be
renewed. This problem afflicts all coatings developed to date. To
prevent this occurrence, water-soluble materials in anti-icing
coatings of the invention are bonded chemically to the surface.
[0020] Generally, coating layers of any type will be subject to
erosion due to wind, particles such as sand, and water erosion.
Bonding the coating layer to the underlying surface will reduce
such erosion but will not prevent it altogether. The selection of a
particular anti-icing coating will therefore be based generally on
considerations of stability and effectiveness of the anti-icing
layer, its cost, the cost of coating of the aircraft or other
substrate, and the stability of the coating.
[0021] The coatings of the present invention are highly efficient
since they are not leachable or soluble by rain or icy water, and
since they are chemically bonded to the substrate, they are not
susceptible to being washed from the substrate during normal
cleaning operations.
[0022] The anti-ice coating material of the present invention
comprises chemically-bonded chains of polymeric material derived
from monomers containing a multivalent element (MVE) such as
carbon, silicon, titanium, zirconium or similar material. In a
typical configuration, the active nano-layer of the MVE, denoted M,
is bonded to the surface and to two other atoms via oxygen atoms. A
fourth bond of the MVE is typically used to bind a radical R that
can interact with water. Such radicals can for example include
groups such as hydroxyls, OH; carbonyls, CO; ethers, C--O--C--; and
the like. The distance between two adjacent MVEs limits the "size"
of aggregates of atoms that can fit between them, while the nature
of the radical R dictates the way in which water will interact with
the surface.
[0023] The invention therefore contemplates materials that can be
bound to a solid surface to confer anti-icing properties to the
surface, as well as various methods to chemically bind anti-icing
compounds to the surface. The methods of the invention enhance the
strength and the density of chemical bonds between the anti-icing
coatings and the solid surface.
[0024] Classes of compounds according to the invention that are
effective in reducing icing include (i) polyethers, such as those
that include one or more [--C2H4-O] groups, (ii) polyhydroxy- or
polyol-containing compounds, e.g., glycols, sugars and other
saccharides, polyvinyl alcohol and polyhydroxyl polymers such as
polyethylene glycol, (iii) poly-amino compounds, including
poly-amino polymers where the amino group is a part of a ring, and
(iv) multi-carboxylic compounds including polycarboxylic compounds
and the salts of such compounds, such as the alkaline and alkaline
earth salts of these compounds.
[0025] In accordance with the present invention, anti-icing
compounds are bound chemically to the surface to be protected
against icing. This gives such compositions a much greater
stability than water-soluble materials that are used as coatings
only. The compositions of the present invention in specific
embodiments include polyether moieties and/or polyhydroxy
compounds, optionally with additives, with the polyhydroxy and/or
polyether compounds being anchored to the surface via covalent
chemical bonds and/or cross-linked on the surface to form a
two-dimensional layer, or both. Certain polyamines can be used in
place of the polyhydroxy compounds.
[0026] In the use of the coating compositions of the invention,
additional techniques may be employed to improve the stability and
performance of the anti-ice layer, including (i) pre-treating the
surface to create more surface sites where the treating material
can bond chemically, and (ii) adding a layer of a second polyol
material on top of the first layer. The second material may be
bonded chemically to the initial layer to increase the effective
surface concentration of hydroxy, amino or carboxy groups, or the
second material may be coated on the first layer to provide another
layer containing compounds rich in hydroxyl, amino or carboxy
groups.
[0027] The two main functions of the surface pre-treatment are (1)
to increase the number of active sites on the substrate surface on
which the coated nano-layer can bond, and (2) to ensure that the
entire substrate surface is activated and available for
bonding.
[0028] The two main functions of the surface nano-layer coating of
the invention are (1) to place on the substrate surface
chemically-bonded "whiskers" that retain water in a liquid form
that will freeze at a much lower temperature than normal, due to
restrictions on the nucleation of ice crystals, and (2) to confer
the substrate surface with super-hydrophilic properties that permit
water droplets to move on the substrate surface virtually without
friction.
[0029] Many variations are possible in the implementation of the
present invention, as informed by the present disclosure, within
the skill of the art.
[0030] The present invention enables a two-dimensional polymeric
layer to be formed on and chemically bound to a substrate surface.
This layer includes interwoven strands of a polymer that is
periodically covalently bonded to the solid surface, e.g., via
siloxane bonds. In addition, from certain regions of this polymer,
branched structures formed by polyol whiskers (POW) protrude in a
conformation that is somewhat like a brush, as shown below as a
schematic representation of a treated surface.
##STR00001##
[0031] In this schematic representation of the treated surface, the
bonded structural layer is an effective anti-ice layer. Such layer
optionally can be augmented by a secondary overcoat of a polymer
such as polyethylene glycol, (PEG), polyvinylalcohol (PVA), or
polymers containing polyethoxy chains.
[0032] Polymeric whisker structures can be made using compounds of
a multi-valent atom such as silicon, titanium, zirconium, etc. An
example of such a synthesis includes the following reactions with a
hydroxylated surface, S--OH wherein S is the designation of the
surface, and trimethoxy silicon compound(s) such as
R-L-Si(OCH.sub.3).sub.3, wherein L is a linker, e.g., a linker of
the formula --C.sub.nH.sub.2n--. The trimethoxysilane moiety
hydrolyzes in water to yield hydroxy groups. Although the reactions
are shown for trimethoxy silanes, the chemistry is very similar
when other types of substitutions are used. Moreover, elements
other than silicon or carbon may also be used, including titanium,
zirconium, cerium, vanadium and others. For the purpose of
illustration, a tri-"leaving group" silane compound, R-L-SiX.sub.3,
wherein X is methoxy, is described herein. The reaction mechanisms
of the silane compounds are very similar, but the kinetics of the
reactions are different.
[0033] The chemistry of modifying a surface which includes surface
hydroxyls is demonstrated using the trimethoxy silicon compound
R-L-Si(OCH.sub.3).sub.3:
R-L-Si(OCH.sub.3).sub.3+3H.sub.2O.fwdarw.{R-L-Si(OH).sub.3}*(Unstable.
Partial conversion possible)+3CH.sub.3OH (1)
[0034] The reactions between --OH groups on silicon atoms and --OH
groups on the solid surface follow and result in binding of the
silicon atom covalently to the surface. The OH groups formed by the
hydrolysis can react and result in the connection of more monomer
molecules in the form of a chain of --O--Si--O--Si-- where a
linking moiety and the radical R protrude from each Si atom.
[0035] Once the substrate surface is coated with the
chemically-bound "two-dimensional" polymeric material with the R
groups are protruding from it, the surface will appear to external
molecules as being covered with Rs. Although the layer is described
as "two dimensional," in reality it is thicker than a monomolecular
layer. The nano-layer may be 1-20 atoms thick and made out of
interwoven structural strings that are covalently bound to the
surface at different locations. The structure of R groups can be
modified as necessary to give the surface the desired
properties.
[0036] To retard the nucleation of ice it is desirable to have on R
hydroxy or amino groups but the preferred structure of R is etheric
moieties such as --C.sub.2H.sub.4--O--. Such groups act toward
water as solutes and serve three functions: [0037] they retard ice
nucleation and thus allow the incipiency of an ice layer only at a
much lower temperature and supersaturation conditions. [0038] they
retain a very thin layer of liquid water on the solid surface,
which helps ice or snow particles that are deposited on it to slide
away, and [0039] the preferred etheric moieties bond water just
strongly enough to increase the surface slip but not strongly
enough to prevent the removal of condensed ice from the substrate
surface.
[0040] The nature of the R groups is very critical to give the
surface the desired properties. The effectiveness of the coverage
depends on the density of the strands with the functional groups,
i.e., the number of available Rs/unit area, while the strength of
the bonding to the surface depends on the number of covalent bonds
to the surface/unit area. These two functions can be modified
independently of one another to produce optimal surface properties,
within the skill of the art and without undue experimentation.
[0041] In coating the substrate surface with the anti-icing coating
of the invention, the surface preferably is cleaned using soap and
followed by an intensive wash with water, or other cleaning medium
is employed to provide a clean surface. Surfaces that have been
contaminated with oil, grease and other materials of similar
character, may be cleaned with alcohols, ketones, aromatic solvents
and the like, to ensure their cleanliness.
[0042] Suitable functionally-terminated Rs, with groups such as
silanol terminated, vinyl terminated and amino terminated
polydimethylsiloxanes, can be used as anchors to bind highly
hydrophilic functionalities. Preferred groups include ethoxylated
moieties, methoxylated moieties, cyclic compounds like dioxane,
amines, hydroxyls and carboxyls. Other groups may also be
effective, as will be appreciated by those skilled in the art,
based on the disclosure herein.
[0043] The anti-icing compositions of the invention may also
include additives to modify the resistive or dielectric properties
of the coating.
[0044] The coating compositions of the invention can be applied to
a substrate surface such as an aircraft surface, in any suitable
manner imparting anti-icing properties to the surface of the
substrate. In one embodiment, the application procedure for the
coating composition may include the following steps:
cleaning the surface; activating the surface; applying the surface
treatment solution to the surface to form a coating thereon; curing
the coating, and applying the modification solution for R to the
coating.
[0045] After the treatment and the modification of the initial R
functionality, one may add a second layer including materials such
as polyethylene glycol, polyvinyl alcohol, polyacrylic acid, etc.
These materials will remain on the surface for a limited time, and
will assist the anti-ice effect achieved by the primary bonded
layer of anti-icing material.
[0046] The surface activation methods used in the practice of the
invention may be of any suitable type, and may for example include
surface pretreatment steps such as: [0047] 1. pretreating the
surface with aqueous solutions of alkaline base such as sodium
hydroxide, potassium hydroxide, ammonia, etc.; [0048] 2.
pretreating the surface with aqueous solutions of alkaline salt
such as sodium phosphate, sodium carbonate, etc.; [0049] 3.
pretreating the surface with organic or liquid ammonia solutions of
alkali metal or alkali metal conjugates such as sodium naphthalene;
[0050] 4. pretreating the surface with aqueous solutions of
reducing material such as titanium tri-chloride or tin di-chloride;
and/or [0051] 5. pretreating the surface with aqueous solutions of
oxidizers such as nitric acid, solutions of permanganate in dilute
acid or in an alkali, solutions of chromate, hydrogen peroxide or
the like.
[0052] These treatments may be employed independently or in a
sequence in combination with one another. They may for example be
applied at different concentrations and/or temperatures.
[0053] In various illustrative embodiments, activation methods such
as the following can be used: [0054] nitric acid treatment (e.g.,
5%, 25%, or 69%, for an appropriate time, e.g., 5 minutes,
depending on the solid). [0055] sodium tri-phosphate treatment,
which may be carried out at various concentrations, e.g., exposure
for 10 minutes at 22.degree. C. using a solution of 7.5 gram
Na.sub.3PO.sub.4 in 100 ml; [0056] sodium hydroxide treatment,
which may be carried out at various concentrations, e.g., exposure
for 10 minutes at 22.degree. C. using a solution of 10 gram NaOH in
100 ml; [0057] treatment with a solution of 10 grams of sodium
naphthalene in 100 ml tri-ethylene-glycol di-methyl ether for 10
minutes at 22.degree. C. (this solution is particularly useful for
fluorinated polymers); and [0058] treatment with a solution of 2.5%
titanium tri-chloride in 7.5% hydrochloric acid at 22.degree. C.
for 10 minutes.
[0059] The invention thus contemplates an anti-icing composition
layer on a substrate surface, comprising a polymeric layer
chemically bonded to the surface with multiple hydrophilic,
hydroxylic or ionic groups attached to the polymer of the polymeric
layer or to grafted appendages on the polymeric layer.
[0060] Such anti-icing composition layer can be chemically bonded
to the surface by multivalent element-oxygen-to-surface bonds,
wherein the multivalent atom is selected from the group consisting
of silicon, carbon, tin, titanium, germanium, zirconium, hafnium,
vanadium and carbon.
[0061] In one embodiment, the multivalent element is selected from
the group consisting of silicon, titanium and zirconium.
[0062] In another embodiment, the polymeric layer comprises a
polymer formed by monomers containing hydrolysable mono, di or
tri-X-silicones wherein each X is independently selected from the
group consisting of chlorine, bromine, iodine, acrylates,
methacrylates, aryl-sulfonates, alkyl-phosphates, ethylene amines,
aliphatic acids, aliphatic hydroxy acids, alkoxy groups, methoxy,
ethoxy, iso-propoxy, di-silazanes, hydrolysable nitrogen moieties,
hydrolysable sulfur moieties, and hydrolysable phosphorous
moieties.
[0063] The anti-icing composition layer on the substrate surface
may comprise a polymer formed by monomers containing two or more
terminal tri-X-multivalent element groups, wherein X is a
hydrolysable group, or alternatively a polymer formed by monomers
containing a mixture of di-tri-X-multivalent element and
mono-tri-X-multivalent element compounds. The multivalent element
in the monomers containing hydrolysable tri-X-multivalent element
can also be attached to a reactive organic radical, such as for
example, chlorine, bromine, iodine, epoxide, carbonyl, nitrile,
cyano, amine-including aromatic or aliphatic primary, secondary,
tertiary and quaternary amines and their salts, chlorides,
bromides, sulfates, nitrile, amides, esters, ethers, alkoxy,
methoxy, ethoxy, thioalkyl, epoxide, vinyl, phosphine, phosphates,
sulfonic or halo-sulfonic groups.
[0064] The anti-icing composition layer may be formed on a
substrate surface, with the polymeric layer being deposited on the
surface by first partially hydrolyzing a tri-X-multivalent element,
and applying the resulting partially-hydrolyzed mixture to the
surface.
[0065] The anti-icing composition layer may be applied to the
substrate by spraying onto the substrate for coating of the surface
thereof.
[0066] The anti-icing composition layer, once formed, may then have
a secondary coating applied on the polymeric layer to increase its
hydrophilicity. The secondary coating can include multi-hydroxy,
poly-carboxy or poly-amino polymeric compounds selected from the
group consisting of poly vinyl alcohol and its homologs, poly
ethylene glycol and its homologs, polyacrylic acid and its
homologs, polyimines, polyamines and polymeric salts.
[0067] The anti-icing composition layer may be formed on the
substrate surface after such surface is pretreated. The surface may
be pretreated by a technique selected from among:
(a) functionalizing the surface with hydroxy, carboxy, carbonyl,
carbonyls, amino or sulfonic groups to increase bonding of monomers
of the polymeric layer to the surface; (b) contacting the surface
with an alkaline base, e.g., a base selected from the group
consisting of sodium hydroxide, potassium hydroxide, ammonium, and
calcium hydroxide; (c) contacting the surface with an aqueous
solution of an alkaline salt, e.g., a salt including a cation
selected from the group consisting of sodium, potassium, calcium,
lithium, cesium, and rubidium, and an anionic moiety selected from
the group consisting of phosphate, carbonate, sulfide, borate,
acetate, organic sulfonate, and organic phosphate; (d) contacting
the surface with an organic amine; (e) contacting the surface with
an aqueous solution of an oxidizer, e.g., an oxidizer selected from
the group consisting of permanganate, chromate, persulphate,
perphosphate, and peroxide; (f) contacting the surface with a
solution of a metalite complex, e.g., a complex selected from the
group consisting of sodium naphthalene and potassium naphthalene;
and (g) contacting the surface with an aqueous solution of a
reducing agent, e.g., a reducing agent selected from the group
consisting of titanium trichloride and tin chloride.
[0068] The pretreatment in one embodiment comprises a technique
selected from among oxidation of the surface, oxidation of the
surface followed by hydrolysis, introduction of ions onto the
surface via acidic or amino groups, and functionalizing the surface
with carbonyl or epoxide groups.
[0069] In the formation of the anti-icing composition layer on a
substrate surface, wherein the layer includes a reactive
functionality, a second treatment can be used to activate the
functionality, e.g., a reactive organic radical, wherein the
activation comprises one or more of hydrolysis, oxidation and
diazotation. In such instance, a third reaction can be used to
couple a multi-hydroxy compound to the activated functionality,
e.g., activated organic radical, such as etherization,
esterification, diazo-coupling and/or formation of a salt.
[0070] Curing of the anti-icing composition layer on the substrate
surface may be carried out at any suitable conditions. Curing may
for example be carried out with hot air in a temperature range of
25 to 300.degree. C., for a period of from 0 to 120 minutes, in one
embodiment. In another embodiment, the anti-icing composition layer
is cured at temperature in a range of 120-170.degree. C. and
duration of curing is in a range of 5 to 30 minutes.
[0071] When the applied anti-icing composition layer is hydrolyzed
to effect hydrolysis of monomer in the applied film, the monomer
may be hydrolyzed at any suitable conditions, e.g., a pH range of 1
to 8, and/or a temperature range of 0 to 60.degree. C., in an
aqueous solution in which concentration of the monomer is in a
range of from 0.001 to 20% by weight, based on total weight of the
solution.
[0072] The monomer(s) of the anti-icing polymeric layer can be of
any suitable types and varieties. For example, the monomers in
various embodiments of the invention can include monomers such as
N-(3-Triethoxysilyl propyl) gluconamide, tris(acrylic acid)
titanium ethoxylate, 2-[Methoxy(polyethyleneoxy)propyl], and/or
neopentyl(dially)oxy tris(acrylic acid) zirconate.
[0073] Although various aspects, features and embodiments of the
invention have been variously illustratively described, it will be
appreciated that individual features of the disclosure herein may
be utilized in combinations and/or permutative arrangements in
which one or more of such features may be utilized to the exclusion
of others, and that therefore the present disclosure constitutes a
source from which specific features may be isolated and aggregated,
within the scope of the invention.
[0074] The features and advantages of the invention are more fully
appreciated from the ensuing examples, which are not intended to be
in any way limiting, but merely illustrative of the invention in
various specific embodiments thereof.
Example 1
Application of Initial Active Coating
[0075] Surface to be treated: aluminum coupon or coupons of
carbon-fiber reinforced epoxy (CRE). Surface Pretreatment: wash
with soap and water to remove all dirt and oils; if still unclean,
wash with solvent, such as toluene, and then wash with isopropanol
followed by drying. Surface Activation: methods of the type
discussed hereinabove give acceptable results. Material for
Treatment: N-(3-triethoxysilylpropyl) gluconamide in 50% ethanol,
which may optionally be diluted with absolute alcohol or absolute
isopropanol down to 3%. Treating Method: spray the surface with the
solution at ambient temperature and let it stand for at least 3
minutes. Curing the Surface: air drying for 15 minutes followed by
65.degree. C. air for 30 minutes. Testing Method Static technique.
Water droplets, smaller than 50 microliters, are placed on the
sample surface at least 1 mm apart and the sample is cooled to at
least -7.5.degree. C. in water-saturated air for at least three
days. The sample surface is examined to determine if the water has
frozen on it or not; in some cases, a small amount of titanium
dioxide powder (250 mesh) is added to the water to help visualize
and photograph the droplets. Testing Method Dynamic technique. Cool
the surface to about -3.9.degree. C. and expose it to an air stream
at 80 knots (92 miles/hr) carrying 0.4 gm water/m.sup.3 in the form
of droplets having a size of 20 microns at a temperature of
.about.-3.9.degree. C. at an angle of attack of 45 degrees, for a
period of 10 minutes. Tests were conducted with water loading in
the range of 0-1.15 gm/m.sup.3, angles of attack of 6-65 degrees,
temperatures in the range of 20-30.degree. F., and air velocities
of up to 115 knots. Evaluation Criteria If the water droplets do
not freeze on the treated surface but freeze on the surface of a
control sample that was not treated, then the treated surface and
the treatment method are acceptable. The accumulation of ice and
its shapes were examined and compared.
Example 1.1
Treatment of Cleaned Aluminum Coupons
[0076] The treated surface did not permit the water to freeze.
Example 1.2
Treatment of Aluminum Coupons Cleaned with Sodium Phosphate
[0077] There was no meaningful difference between aluminum coupons
cleaned with sodium phosphate and those cleaned with water.
Example 1.3
Treatment of Aluminum Coupons Cleaned with Sodium Phosphate and
Subsequently Oxidized with Concentrated Nitric Acid
[0078] The treated surface resulted in the most uniform coating and
the coating prevented water from freezing on it.
Example 1.4
Treatment of Aluminum Coupons Cleaned with Sodium Phosphate and
Subsequently Oxidized with Concentrated Nitric Acid, Washed and
Following the Treatment with a Coat of Polyethylene Glycol.
(PEG)
[0079] The treated surface resulted in an extremely uniform coating
and the coating prevented water from freezing on it.
Example 1.5
Treatment of Cleaned Epoxy Coupons
[0080] The treated surface did not permit the water to freeze.
Example 1.6
Treatment of Epoxy Coupons Cleaned with Methanol and Subsequently
Oxidized with Sodium Hypochlorite Solution
[0081] The treated surface resulted in the most uniform coating and
the coating prevented water from freezing on it.
Example 1.7
Treatment of Epoxy Coupons Cleaned with Methanol and Subsequently
Oxidized with Hypochlorite Solution, Washed and Following the
Treatment with a Coat of Polyethylene Glycol (PEG)
[0082] The treated surface resulted in an extremely uniform coating
and the coating prevented water from freezing on it.
Example 2
Two-Stage Coating-First Coating with a Simple Silicone Followed by
Reaction of the Vinyl Group With Free Radical Graft
Polymerization
[0083] The treatment in this example refers to both cleaned
aluminum and epoxy surfaces but works more efficiently on
epoxy.
[0084] In this example, (3-acryloxypropyl) trimethoxysilane,
(APTMS),
CH.sub.2.dbd.CHC(O)OCH.sub.2CH.sub.2CH.sub.2Si(OCH.sub.3).sub.3,
was used as the reagent for the first stage of the treatment. A 2%
solution of APTMS in 70% IPA was prepared and its pH was adjusted
with dilute acetic acid to 4.5. The mixture was stirred for 12
minutes and sprayed on the surface.
Example 2.1
[0085] An aqueous solution of 5% ascorbic acid in 8% sodium
carbonate with 0.3% of the catalyst t-butyl-hydroperoxide, and a
second treating reagent of ascorbic acid, is employed. Light helps
the formation of the film at temperatures below 25.degree. C. The
solution must be applied immediately after preparation. Small
amounts of EDTA improve its pot life.
Example 2.2
[0086] An aqueous solution of 5% maleic acid in 8% sodium carbonate
with 0.3% of the catalyst t-butyl-hydroperoxide, and a second
treating reagent of ascorbic acid, are employed. Light helps the
formation of the film at temperatures below 25.degree. C. The
solution must be applied immediately after preparation. Small
amounts of EDTA improve its pot life. Fumaric acid reacts in a
similar way.
Example 2.3
[0087] An aqueous solution of 1-5% partially dehydroxylated sugar,
(PDHS), in acidic or basic pH, with 0.3% of the catalyst
t-butyl-hydroperoxide and the second treating reagent ascorbic
acid. Light helps the formation of the film at temperatures below
25 C. The solution must be applied immediately after preparation.
Small amounts of EDTA improve its pot life.
[0088] The PDHS is obtained by adding 10 grams anhydrous zinc
chloride to 30 grams sugar in 50 ml 100% IPA and warming the
mixture to 60.degree. C. for 30 minutes while stirring constantly.
A slight discoloration may occur. The solution is then treated with
10 grams of sodium carbonate in 20 ml water and filtered to remove
the white zinc carbonate formed. The solution has to be stored in
the dark.
Example 2.4
[0089] A 0.4 molar solution of sodium acrylate with 0.2 molar
triethanol amine in 5% hydrogen peroxide was prepared and warmed up
to 95 C. Cupric sulfate was added to 3000 ppm Cu.sup.+2 and the
solution was quickly sprayed on the surface treated with APTMS. The
spraying was repeated three times at 15 minute intervals.
[0090] Droplets of water of 50 microliters in size did not freeze
on the surface after exposure to -7.5.degree. C. for three days in
air saturated with water vapors.
Example 3
Two Stage Coating. First Coating as an Aromatic Amino Silicone,
Second Coating applied by Diazotizing the Amino Group With a
Nitrite and Following with a Reaction with Hydroxylated Aromatic
Compound
[0091] The treatment in this example refers to both cleaned
aluminum and epoxy surfaces but works more efficiently on
epoxy.
[0092] In all the tests described p-tri-methoxy-aniline (TMA) was
used, but other tri-X silanes, or other aromatic amines, may also
be used equally well. The 2% TMA solution in 71% IPA was applied to
the surface after adjusting its pH to 4.5 and stirring it 15
minutes. The surface was then treated with 5% solution of sodium
nitrite in water, pH of 4.5, adjusted using acetic acid. (Citric
acid works equally well).
Example 3.1
Using a Hydroxy-Terminated Multi-Ethoxide in Aqueous Solution
[0093] A 3% solution of p-tri-ethoxy-phenol at 40.degree. C. was
sprayed on the surface and let dry.
Example 3.2
Using a Hydroxy-Terminated Multi-Ethoxide in Aqueous Solution with
a Secondary Coating of Poly-Vinyl-Alcohol
[0094] The surface obtained in Example 3.1 was further sprayed with
3% poly-vinyl-alcohol, at 50.degree. C. and the solution was
allowed to dry. This treatment gave excellent results both for
aluminum and epoxy surfaces.
Example 4
Using the Ethoxylated Silicon Compound
2-[methoxy(polyethylenoxy)propyl]-trimethoxysilane as the First
Treatment
[0095] The treatment in this example refers to both cleaned
aluminum and epoxy surfaces, but works more efficiently on epoxy.
The results obtained were excellent and the treated surface was
relatively stable over three icing cycles.
[0096] The following examples use titanate compositions.
Example 5
Single Initial Active Coating
[0097] Surface to be Treated: Aluminum coupon or coupons of
carbon-fiber reinforced epoxy (CRE). Surface Pretreatment: Wash
with soap and water to remove all dirt and oils, followed by a wash
with a solvent such as toluene and then with isopropanol followed
by drying. Surface Activation: Previously described surface
activation methods give acceptable results. Treating material: 0.1%
Tris-acrylic-titanium tri-ethoxylate-methoxide (TATEM) in 91% IPA
was used in all examples with titanium. Treating Method: Spray the
surface with the solution at ambient temperature and let it stay
there for at least 15 minutes. Curing the Surface: Blow hot air at
65 C for 30 minutes. Testing Method: Water droplets, smaller than
50 microliters, are placed on the sample surface at least 1 mm
apart and the sample is cooled to at least -7.5.degree. C. in
water-saturated air for at least three days. The sample surface is
examined to determine if the water froze on it or not. In some
cases, a small amount of titanium dioxide powder (250 mesh) is
added to the water to help visualize and photograph the droplets.
Evaluation Criteria: Static. If the water droplets do not freeze on
the treated surface but freeze on the surface of a control sample
which was not treated, then the treated surface and the treatment
method are acceptable. Testing Method: Dynamic. Cool the surface to
about -3.9.degree. C. and expose it to air stream at 80 knots, (92
miles/hr) carrying 0.4 gm water/m.sup.3, with droplets size of 20
microns at .about.-3.9.degree. C. at an angle of attack of 45
degrees, for a period of 10 minutes. Tests were conducted with
water loading in the range of 0-1.15 gm/m.sup.3, angles of attack
of 6-65 degrees, temperatures in the range of 20-30.degree. F., and
air velocities of up to 115 knots. Evaluation Criteria: If the
water droplets do not freeze on the treated surface but freeze on
the surface of a control sample that was not treated, then the
treated surface and the treatment method are acceptable. The
accumulation of ice and its shapes were examined and compared.
Example 5.1
Use of a Titanate Compound After Surface Activation with Sodium
Hydroxide Solution
[0098] A 2.5 Molar solution of sodium hydroxide was placed on the
surface for 10 minutes at room temperature. After this
pretreatment, the surface was treated with a 0.1% solution of
TATEM. This was allowed to dry at room temperature for 15 minutes,
and then cured at 65 degrees Celsius for 30 minutes. This treatment
provided the lowest contact angle of any surface prepared during
the testing.
Example 5.2
[0099] Use of Titanate Compound After Pretreatment of a Surface
Using a Phosphate Solution
[0100] A 10% solution of tribasic sodium phosphate was placed on
the surface for 10 minutes at room temperature. After this
pretreatment, the surface was treated with a 0.1% solution of TATEM
in 91% isopropyl alcohol. This was allowed to dry at room
temperature for 15 minutes, and then cured at 65 degrees Celsius
for 30 minutes.
Example 5.3
Use of Titanate Compound After Pretreatment of a Surface Using a
Reduction Step
[0101] A 10% solution of titanium (III) chloride was placed on the
surface for 10 minutes at room temperature. After this
pretreatment, the surface was treated with a 0.1% solution of TATEM
in 91% isopropyl alcohol. This was allowed to dry at room
temperature for 15 minutes, and then cured at 65 degrees Celsius
for 30 minutes.
Example 5.4
Use of Titanate Compound After Pretreatment of a Surface Using an
Oxidation Step
[0102] A 5% solution of hydrogen peroxide was placed on the surface
for 10 minutes at room temperature. After this pretreatment, the
surface was treated with a 0.1% solution of TATEM in 91% isopropyl
alcohol. This was allowed to dry at room temperature for 15
minutes, and then cured at 65.degree. C. for 30 minutes.
Example 6
Use of the Zirconium Compound neopentyl(diallyl)oxy Triacryl
Zirconate, (NPDATAZ), after Pretreatment of a Surface Using Alkali
Solution
[0103] A 2.5 Molar solution of sodium hydroxide was placed on the
surface for 10 minutes at room temperature. After this
pretreatment, the surface was treated with a 0.1% solution of TATEM
in 91% isopropyl alcohol. This was allowed to dry at room
temperature for 15 minutes, and then cured at 65 degrees Celsius
for 30 minutes. The results with the zirconate were not as
definitive as with the titanates.
[0104] While the invention has been described herein with reference
to specific features, aspects and embodiments, it will be
appreciated that the invention is not thus limited, but rather
extends to and encompasses numerous variations, modifications and
other embodiments, such as will suggest themselves to those of
ordinary skill in the art, based on the disclosure herein.
Accordingly, the invention is intended to be broadly construed to
encompass such variations, modifications and other embodiments, as
being within the spirit and scope of the invention as hereinafter
claimed.
* * * * *